Big Bang Nucleosynthesis and Particle Physics

Transcription

1 New Generation Quantum Theory -Particle Physics, Cosmology and Chemistry- Kyoto University Mar Big Bang Nucleosynthesis and Particle Physics Masahiro Kawasaki (ICRR & Kavli IPMU, University of Tokyo)

2 1. Introduction History of Big Bang Model Discovery of comic expansion by Hubble in 1929 Gamov proposed the hot big bang model of the Universe in 1946 Two predictions Existence of cosmic microwave background radiation as relic of photons which were in thermal equilibrium Helium 4 is synthesized in the hot universe Discovery of cosmic microwave background in 1965 Big bang nucleosynthesis successfully accounts for the present abundances of He4 and D Hot Big Bang Model is established 2

3 1. Introduction BBN ( Big Bang Nucleosynthesis ) Cosmological process where light elements are synthesized at t=1sec ~ 1000sec (T=1-0.01MeV) in the early universe Its success strongly supports the big bang model BBN determines baryon density of the Universe Goal which baryogenesis must achieve BBN is very sensitive to physical conditions at T~ 1MeV Prove to the early universe Unstable particles, Dark matter properties.. 3

4 Today s Talk 1. Introduction 2. Standard BBN 3. BBN constraints on unstable particles 4. BBN constraints on annihilation of dark matter 5. Conclusion 4

5 1.1 Standard Big Bang Nucleosynthesis (BBN) In the early universe ( T= MeV ) 2p +2n! 4 He + small D 3 He 7 Li 1. Initial Condition ( T > 1MeV ) p and n interchange via weak interaction ν e + n p + e e + + n p + ν e n p + e + ν e Reaction Rate Γ σvn e G 2 F T 2 T 3 G 2 F T 5 5

6 Γ (reaction rate) >> H (expansion rate) Chemical equilibrium µ νe + µ n = µ p + µ e n n n p µ n = µ p eq = exp Q T n = g ( mt 2π Q = m n n e n e + = 1 3 µ et 2 = n p µ e /T 1(( n e n e + n ) µ /T 1 (assumption) ) 3/2 exp[ (m µ)/t ] m p =1.293 MeV Γ = H weak interactions freeze out n n n p exp ( QTf ) 1 7 T f 1 MeV freeze-out temp. 6

7 n/p T(MeV ) 0.1 Almost all neutrons that exist at that time are synthesized into He4 4 He H + 4 He = 4(n n/2) =2 n n/n p 0.25 n n + n p 1+n n /n p 7

8 MeV < T < 1 MeV p + n! D + n γ n B n B T 0.1 MeV n γ (E γ > 2.22MeV) p + n! D + n Q d = 2.22 MeV Produced D is destroyed D +! p + n 3. T < 0.1 MeV D + D 3 He + n 2.22MeV 4 He + small amount of D, 3 He, 3 H E 3 He + n 3 H + D 3 H + p 4 He + n ( 3 H 3 He + e + e, 1/2 12yr) 8

9 Heavier Light Elements? No No stable nuclei with A=5 or 8 Coulomb Barrier But tiny amount of Li7 4 He + 3 H! 7 Li + 4 He + 3 He! 7 Be + abundances n He4 D He3 Be 7 T 7 Be + e! 7 Li + e Li T(MeV) Abundances of Light Elements only depend on baryon-to-photon ratio η B n B n γ 9

10 Prediction vs Observation Abundance Y p = A H = n A n H 4 He H + 4 He Baryon-photon ratio D/H observation B Lithium problem 10

11 Observational abundances of light elements He4 [ Extragalactic HII region ] Y p = ± Y p = ± D [ Damped Ly alpha system ] Izotov, Thuan, Guseva (2014) Aver, Olive, Skillman (2015) (D/H) p =(2.53 ± 0.04) 10 5 Cooke et al (2013) Li7 [ Metal poor halo stars ] ( 7 L/H) p =(1.6 ± 0.3) Sbordone et al (2010) Li6 [ Metal poor halo stars ] ( 6 Li/ 7 Li) p < 0.05 Asplund et al, (2006) He3 [Solar system ] ( 3 He/D) p < 0.83 ± 0.27 Geiss, Gloeckler (2003) 11

12 D abundance Lyman α, β, γ, δ... absorption in QSOs spectrum HI cloud observer DLyα Quasar F HLyα λ Lyα 1216Å (1+z) λ 0.027% deviation 12

13 DLAS at z abs = toward QSO SDSS J Cooke et al, (2013) 13

14 3. BBN constraints on unstable particles Long-lived unstable particles might spoil success of BBN High energy particles from decay destroy light elements Radiative decay ( photons, electrons ) Hadronic decay ( quarks, gluons ) Candidates Gravitino ( SUSY partner of graviton ) Moduli fields ( predicted in superstring ) Dark matter annihilation can also produce high energy particles which destroy light elements 14

15 3.1 Radiative decay and BBN Radiative decay Electromagnetic shower + BG e + + e e ± + BG e ± + + BG + Many soft photons 2.2MeV (T 20MeV (T Destroy light elements High energy photons X 10keV) 1keV) log 10 [f/(gev 2 )] ϵ γ > m 2 e/22t ε γ0 =100GeV + BG + 10eV 1keV Energy (GeV) + BG e + + e T=100keV MK, Moroi (1995) 15

16 Destruction of light elements D + n + p [2.2MeV] T + D + n [6.2MeV] 3 He + D + p [5.5MeV] 4 He + T + n [19.8MeV] 4 He + 3 He + n [20.5MeV] 4 He + D + n + p [26.1MeV] Non thermal production of D and He3 Non thermal production of Li6 T + 4 He 6 Li + n [4.0MeV] 3 He + 4 He 6 Li + p [4.8MeV] Dimopoulos et al (1989) Jedamzik (2000) 16

17 Constraint on radiative decay Y X n X s (s ' 7n ) E vis : injected energy He3/D gives the most stringent constraint 17

18 3.2 Haronic decay and BBN Decay into gluons and/or quarks Hadronic decay takes place even if main decay is radiative Two effects on BBN X B h 1 g g quarks, gluons produced pions and kaons changes n/p ratio ( t ~ 1sec ) + + n! p p! n + 0 produced n and p destroy light elements ( t > 100 sec) energetic hadrons hadron int. hadrodissociation X B h α/4π change n/p destruction & production of Light elements q q 18

19 Constraint on hadronic decay Y X n X s (s ' 7n ) E vis : injected energy D/H ( τ < 107 sec) or He3/D (τ > 10 7 sec) gives the most stringent constraint 19

20 3.3 Gravitino Problem Supersymmetry (SUSY) Hierarchy Problem Keep electroweak scale against radiative correction Coupling Constant Unification in GUT SUSY particles quark lepton photon Gravitino superpartner of graviton Gravitino ψ 3/2 squarks slepton photino Graviton mass m 3/2 1 TeV α i α 1-1 α 2-1 α µ (GeV) SUSY (a) MSSM 20

21 Gravitino production Gravitinos are produced during reheating after inflation n 3/2 n T R GeV Bolz, Brandenburg, Buchmüller (2001); MK, Moroi (1995) T R :ReheatingTemperature q q g g ψ 3/2 n 3/2 /n γ σn q t (1/M 2 p )T 3 R(M p /T 2 R) T R /M p Gravitino abundance is proportional to reheating temperature Big Bang (reheating) sec 1sec 10sec 1000sec 0.4Myr Present Inflation Neutrino Decoupling BBN Recombination Structure Formation opaque Cosmic Microwave Background Rad. 21

22 Gravitino decay Gravitino decay Radiative decay e.g. τ(ψ 3/2 γ + γ) sec Hadronic decay e.g. τ(ψ 3/2 g + g) sec 3/2 + ( m3/2 ) 3 100GeV 3/2 g + g ( m3/2 ) 3 100GeV ψ 3/2 ψ 3/2 γ γ g g Decay Products (photons, hadrons) Serious effects on BBN Stringent constraint on TR Y 3/2 n 3/2 s T R GeV Ellis, Nanopoulos,Sarkar (1985) Reno, Seckel (1988) Dimopoulos et al (1989) MK, Moroi (1995)

23 Constraint on reheating temperature MK Kohri Moroi Yotsuyanagi (2008) Reheating temperature T R should be less than ~ 10 6 GeV for m3/2 = TeV 23

24 4. Constraint on annihilation of dark matter Dark Matter There is a large amount of dark matter in our universe than luminous matter (= baryons) Evidences Rotation curve of galaxies Cosmic microwave radiation (CMB) e.g. Planck (2015) CMB data fit to ΛCDM model with DM =0.265 B =0.049 b h 2 = ± c h 2 = ± c ' 5 b (Dark matter) ~ 5 (baryon) 24

25 4.1 Constraint on annihilation of dark matter Dark matter particles annihilate in the early universe DM + DM e + + e -, q + q Particles produced in DM annihilation affects BBN Constraints on annihilation cross section If DM is thermal relic (once in thermal eq.) h vi ' cm 3 /s observed DM abundance Constraint (assuming DM density) DM+DM e + + e - Hisano, Kawasaki, Kohri, Moroi, Nakayama (2009) Similar to radiative decay annhilate into e + e - 25

26 4.1 Constraint on annihilation of dark matter Constraint (assuming DM density) DM+DM q + q D gives the stringent constraint If DM is thermal relic m & GeV! q q per bounds at 95% C.L. on the annihilation cross section into t Kawasaki, Kohri, Moroi, Takaeshu (2015) 26

27 4.2 Constraint on annihilation of winos Wino is SUSY partner of W boson Constraint (assuming DM density) Wino is DM in some SUSY models which are favored by 126GeV Higgs D gives the stringent constraint 320 GeV. m. 2.3 TeV m & 2.7 TeV Kawasaki, Kohri, Moroi, Takaeshu (2015) Wino 27

28 5. Conclusion BBN is an important process whose success supports the hot big bang model Measurements of light elements can make a precise determination of the baryon density of the universe Abundances of light elements synthesized by BBN are sensitive to conditions at T~ 1MeV, so BBN can be used as a probe to the early universe and give various constraints on particle physics (e.g. unstable particles and annihilation of dark matter) 28

29 Backup 29